1. Field of the Invention
The present invention relates to repairing concrete and, more particularly, relates to a method and apparatus for joining concrete sections together.
2. Discussion of the Related Art
Over time, cracks can develop within concrete structures which, if left unrepaired, can result in failure of the structure. To prevent such an occurrence without having to replace an entire slab, damaged slabs are often repaired by cutting a damaged section away from a preexisting concrete section, and by pouring new concrete in its place. However, new concrete does not always bond perfectly with the preexisting concrete, and cracks can propagate in the joint between the two sections.
Previous methods have been implemented to repair concrete structures and maintain the mechanical connection between a new concrete section and a preexisting concrete section. One repair method involves first removing defective concrete and drilling holes in the preexisting concrete using a rotary impact hammer drill. An adhesive is then placed into the holes, and reinforcing bars are inserted such that the bars extend beyond the outer wall of the preexisting concrete and are generally perpendicular to the joint between the preexisting concrete section and the gap defining the area where the new concrete is to be poured. The new concrete is then poured adjacent the preexisting concrete such that the ends of the reinforcing bars extend into the new concrete and bond with the new concrete when it cures. Therefore, when the new concrete cures, it will be joined to the preexisting concrete via the reinforcing bars.
Additionally, when attaching external fixtures to preexisting concrete sections, holes are drilled using, e.g., a standard rotary drill, and anchors are either bonded or friction-fitted within the holes. The external fixtures are then mounted onto the anchors.
Several disadvantages are associated with these methods of repair and attachment. For example, drilling multiple holes into the existing concrete is a slow and labor intensive process. Additionally, the vibrations associated with the drilling can cause an entire section of concrete to fail. Moreover, once a hole is drilled, it must be subsequently cleaned of dust and concrete particles in order to permit the adhesive to bond to the concrete. In addition, cracks can form over time in the joint between the new section and the preexisting concrete. As moisture seeps down these cracks, a metallic reinforcing bar will rust, corrode, and subsequently fail, thereby necessitating further repair. Additionally, a phenomenon known in the industry as "burping" may occur, whereby air pockets become trapped within the hole once the reinforcing bar is installed, thereby preventing at least a portion of the adhesive from bonding with the reinforcing bar. This can lead to premature failure of the reinforced joint.
In another type of concrete structure, for example a parking garage structure, a concrete driveway is disposed above T-shaped concrete beams that are typically joined together by metal clips. As cracks form in the concrete, however, moisture seeps into the supports and corrodes the metal clips, ultimately causing them to fail. One previous method of repairing this type of structure involved welding or bolting a supplemental joining apparatus to both supports, thereby retaining them together. This method, however, is expensive and labor intensive. Additionally, the repair is aesthetically unappealing. Another method of repair involved cutting through the concrete to access and replace the failed metal clip. Again, this process is labor intensive and expensive.
The need has therefore arisen to provide an improved method and apparatus for repairing and/or adding external fixtures to concrete structures that retains the integrity of the preexisting concrete, that is not labor intensive, that does not corrode over time, and that resists premature failure.